1. Field of the Invention
The present invention relates to a fiber reinforced resin gear formed using a resin which contains reinforcing fibers, a fiber reinforced resin rotary body, and a method of forming the fiber reinforced resin gear and the fiber reinforced resin rotary body by injection molding.
2. Description of the Related Art
Conventionally, in a power transmission mechanism of various machines such as an automobile, an industrial machine or a copier, a fiber reinforced resin gear having high strength is used in place of a metal-made gear. Such a fiber reinforced resin gear is manufactured by injecting a molten resin which contains reinforcing fibers such as glass fibers or carbon fibers into the inside of a cavity. However, it has been known that such a fiber reinforced resin gear has a drawback in that the difference in shrinkage ratio attributed to non-uniformity of the fiber orientation of reinforcing fibers is generated so that roundness of the fiber reinforced resin gear after forming is deteriorated.